In this paper

an improved signal injection method is proposed to solve the problem that the traditional method does not consider the zero sequence voltage in the measurement of the capacitance current of the neutral point. This method is used to calculate the ground capacitance of the system by measuring the voltage value of the open delta of the voltage transformer under different conditions through the Devenan equivalent circuit model which considers the transformer winding leakage reactance and the zero sequence voltage system. The method is simple in operation and has high measurement precision. The accuracy and applicability of the proposed method are verified by the simulation results and practical application.